Display device

ABSTRACT

A display device includes a flexible substrate having a display region including a plurality of pixels, each of the plurality of pixels having a pair of electrodes and a display element therebetween; a first electrode layer provided on the plurality of pixels; a second electrode layer provided on the first electrode layer; a third electrode layer provided on the second electrode layer; a piezoelectric material layer provided between the first electrode layer and the second electrode layer; and a flexible material layer provided between the second electrode layer and the third electrode layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority from theprior Japanese Patent Application No. 2016-099375, filed on 18 May 2016,the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to a display device, and specifically, toa display device including a touch sensor, a press senor and a bendingsensor.

BACKGROUND

An organic electroluminescence display device (hereinafter, referred toas an “organic EL display device”) includes a light emitting element ineach of pixels, and controls the light emission of each individual lightemitting element to display an image. A light emitting element includesa pair of electrodes, one of which is an anode electrode and the otherof which is a cathode electrode, and a layer containing an organic ELmaterial (hereinafter, referred to also as a “light emitting layer”)held between the pair of electrodes. When electrons are injected fromthe cathode electrode into the light emitting layer and holes areinjected from the anode electrode into the light emitting layer, theelectrons and holes are recombined. Extra energy released by therecombination excites and then de-excites light emitting molecules inthe light emitting layer. As a result, light is emitted.

In an organic EL display device, the anode electrode of each of thelight emitting elements is provided as a pixel electrode in each of thepixels. The cathode electrode is provided over a plurality of pixels asa common electrode supplied with a common potential. In the organic ELdisplay device, a potential of the pixel electrode is applied to thecorresponding pixel with respect to the potential of the commonelectrode, so as to control the light emission of the pixel.

Recently, a technology of providing a sensor detecting a touch and asensor detecting a pressure (press) in a flexible organic EL displaydevice is has been developed.

For example, Japanese PCT National-Phase Laid-Open Patent PublicationNo. 2013-529803 discloses a touch screen display sensor including atransparent touch detection element located on a surface of atransparent substrate and a force detection element located in thetransparent touch detection element. The force detection elementincludes two sets of micromesh bands and a pressure-sensitive materialprovided between the micromesh bands. The micromesh bands each include aline formed of a metal conductive material. The sets of micromesh bandsare separated from each other and put on planes substantially parallelto each other.

SUMMARY

A display device in an embodiment according to the present inventionincludes a flexible substrate having a display region including aplurality of pixels, each of the plurality of pixels having a pair ofelectrodes and a display element therebetween; a first electrode layerprovided on the plurality of pixels; a second electrode layer providedon the first electrode layer; a third electrode layer provided on thesecond electrode layer; a piezoelectric material layer provided betweenthe first electrode layer and the second electrode layer; and a flexiblematerial layer provided between the second electrode layer and the thirdelectrode layer.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a perspective view showing an external structure of a displaydevice in an embodiment according to the present invention;

FIG. 2 is a circuit diagram showing a circuit configuration of thedisplay device in an embodiment according to the present invention;

FIG. 3 is a plan view showing a structure of a sensor portion of thedisplay device in an embodiment according to the present invention;

FIG. 4A is a cross-sectional view showing a structure of the displaydevice in an embodiment according to the present invention;

FIG. 4B is an enlarged cross-sectional view showing the structure of thedisplay device in an embodiment according to the present invention;

FIG. 4C is an enlarged cross-sectional view showing the structure of thedisplay device in an embodiment according to the present invention;

FIG. 5 shows a circuit configuration of the sensor portion of thedisplay device in an embodiment according to the present invention;

FIG. 6 shows a method for driving the sensor portion of the displaydevice in an embodiment according to the present invention;

FIG. 7A is a perspective view showing an application example of thedisplay device in an embodiment according to the present invention;

FIG. 7B is a perspective view showing an application example of thedisplay device in an embodiment according to the present invention;

FIG. 8 is a plan view showing a structure of a sensor portion of adisplay device in an embodiment according to the present invention;

FIG. 9 is a cross-sectional view showing a structure of the displaydevice in an embodiment according to the present invention; and

FIG. 10 shows an application example of the display device in anembodiment according to the present invention.

DESCRIPTION OF EMBODIMENTS

A technology of providing a sensor detecting a touch and a sensordetecting a pressure (press) in a flexible organic EL display device hasbeen developed. However, there is no prior example of technology offurther providing a sensor detecting a bending.

For providing sensors detecting a touch, a pressure (press) and abending in a flexible organic EL display device, there is a problem thatdetection signals need to be separated from each other.

The present invention has an object of providing a display deviceincluding sensors detecting a touch, a pressure (press) and a bendingand allowing detection signals to be separated from each other.

Hereinafter, some embodiments of the present invention will be describedin detail with reference to the drawings. A display device according tothe present invention is not limited to any of the following embodimentsand may be carried out in various modified forms. In all theembodiments, the same elements will bear the same reference signs. Inthe drawings, the relative sizes may be different from the actualrelative sizes for the sake of illustration, or a part of the componentsmay be omitted.

In this specification, the terms “up”, “down” and the like used for thedrawings each represent a positional relationship between a componentthat is a target of attention and another component. In thisspecification, as seen in side view, a direction from a surface of afirst substrate 104 (described below) toward a light emitting element146 is defined as “upward”, and an opposite direction thereto is definedas “downward”. In this specification and the claims, an expression thatone element is located “on” another element encompasses a case where theone element is located directly on another element in contact with theone element and also a case where the one element is located on anotherelement with still another element being provided between the oneelement and another element, unless otherwise specified.

Embodiment 1 [External Structure]

FIG. 1 is a perspective view showing an external structure of a displaydevice 100 in an embodiment according to the present invention. Withreference to FIG. 1, the external structure of the display device 100will be described.

The display device 100 in this embodiment includes an array substrate102, a sealing layer 132, a first electrode layer 134, a secondelectrode layer 136, a third electrode layer 138, a piezoelectricmaterial layer 142, a flexible material layer 140, a protective film106, and a plurality of connection terminals 112.

The array substrate 102 includes at least the first substrate 104 and aplurality of pixels 110. The first substrate 104 is flexible. Such aflexible substrate is formed of a resin material although specificmaterials will be described below. On the first substrate 104, a displayregion 104 a and a terminal region 104 b are provided.

The plurality of pixels 110 are arrayed in the display region 104 a onthe first substrate 104. In this embodiment, the plurality of pixels 110are arrayed in a matrix. Although not shown in FIG. 1, the plurality ofpixels 110 each include a pixel circuit 126 (FIG. 2) including at leasta selection transistor, a driving transistor 144 (FIG. 4C) and the lightemitting element 146 (FIG. 4C).

The sealing layer 132 is located on the display region 104 a and coversthe plurality of pixels 110. The sealing layer 132 is provided in orderto prevent entrance of moisture or the like into the plurality of pixels110 in the display device 100 from outside of the display device 100.

On the sealing layer 132, the first electrode layer 132, thepiezoelectric material layer 142, the second electrode layer 136, theflexible material layer 140 and the third electrode layer 138 arestacked in this order. As described below in detail, the first electrodelayer 134, the second electrode layer 136 and the piezoelectric materiallayer 142 are included in a bending sensor. The second electrode layer136, the third electrode layer 138 and the flexible material layer 140are included in a press sensor. The third electrode layer 138 isincluded in a touch sensor.

The plurality of connection terminals 112 are provided in the terminalregion 104 b. The terminal region 104 b is located along one end of thefirst substrate 104. The plurality of connection terminals 112 areconnected with a wiring substrate 114 a and a wiring substrate 114 b.The wiring substrate 114 a connects a device outputting a video signal,a power source or the like and the display device 100 to each other. Thewiring substrate 114 b connects a device driving various sensors, apower source or the like and the display device 100 to each other.

The external structure of the display device 100 in this embodiment isdescribed above. Now, with reference to the drawings, a circuitconfiguration of the display device 100 in this embodiment will bedescribed.

[Circuit Configuration for Display]

FIG. 2 is a circuit diagram showing a circuit configuration of thedisplay device 100 in this embodiment. FIG. 2 shows the circuitconfiguration for display. A circuit configuration provided for varioussensors in the display device 100 will be described below

The display device 100 in this embodiment includes a driving circuit,the plurality of pixel circuits 126, a plurality of scanning signallines 128, and a plurality of video signal lines 130.

The driving circuit includes a control circuit 116, a scanning linedriving circuit 118, a video line driving circuit 120, a driving powersource circuit 122, and a reference power source circuit 124. Thedriving circuit drives the pixel circuits 1 26 respectively provided inthe plurality of pixels 110 to control the light emission of theplurality of pixels 110.

The control circuit 116 controls the operation of the scanning linedriving circuit 118, the video line driving circuit 120, the drivingpower source circuit 122 and the reference power source circuit 124.Specifically, the control circuit 116 outputs a timing signal used fordriving the scanning line driving circuit 118 and the video line drivingcircuit 120, supplies a video signal to the video line driving circuit120, and determines the potential to be output from each of the drivingpower source circuit 122 and the reference power source circuit 124.

The scanning line driving circuit 118 is connected with the plurality ofscanning signal lines 128. The plurality of scanning signal lines 128are respectively provided for horizontal lines of the plurality ofpixels 110 (pixel rows). The scanning line driving circuit 118sequentially selects the plurality of scan signal lines 128 inaccordance with the timing signal input from the control circuit 116.

The video line driving circuit 20 is connected with the plurality ofvideo signal lines 130. The plurality of video signal lines 130 arerespectively provided for vertical lines of the plurality of pixels 110(pixel columns). The video line driving circuit 120 receives a videosignal input from the control circuit 116, arid when the scanning linedriving circuit 118 selects a scanning signal 128, supplies a voltage inaccordance with the video signal of the selected pixel row to theplurality of video signal lies 130.

The driving power source circuit 122 is connected with driving powersource lines (not shown) respectively provided for the pixel columns.The driving power source circuit 122 supplies an electric current usedto allow the pixels 110 to emit light in accordance with the input videosignal.

The reference power source circuit 124 is connected with a referencepower source line (not shown) provided commonly to the plurality ofpixels 110. The reference power source circuit 124 supplies a constantpotential to the common electrode (cathode electrode) of the lightemitting element provided in each of the pixel circuits 126.

The circuit configuration of the display device 100 in this embodimentis described above. Now, with reference to the drawings, the structureof the display device 100 in this embodiment will be described indetail.

FIG. 3 is a plan view showing a structure of a sensor portion of thedisplay device 100 in this embodiment. FIG. 4A is a cross-sectional viewshowing the structure of the display device 100 in this embodiment, andshows a cross-section taken along line I-I′ in FIG. 3. FIG. 4B is anenlarged cross-sectional view showing a structure of a touch sensorportion A (FIG. 4A) in the display device 100 in this embodiment. FIG.4C is an enlarged cross-sectional view showing a structure of a pixelportion B (FIG. 4A) in the display device 100 in this embodiment. InFIG. 4A, the pixels are shown larger than the actual size with respectto the other elements, for the sake of illustration. In actuality, thepixels 110 are sufficiently smaller than patterns of the third electrodelayer 138 described below.

As shown in FIG. 1, the display device 100 in this embodiment includesthe first substrate 104, the plurality of pixels 110, the sealing layer132, the first electrode layer 134, the second electrode layer 136, thethird electrode layer 138, the piezoelectric material layer 142, theflexible material layer 140, and the protective film 106.

As shown in FIG. 1, the first substrate 104 has the display region 104 aand the terminal region 104 b thereon. In this embodiment, the firstsubstrate 104 is a flexible substrate. The flexible first substrate 104is formed of a resin material. A preferably usable resin material is apolymer material including imide bond in a repeat unit. For example,polyimide is usable as the resin material. Specifically, the firstsubstrate 104 is a film substrate formed of polyimide molded into asheet. With such a structure, the array substrate 102 is entirelyflexible.

The plurality of pixels 110 are arrayed in the display region 104 a onthe first substrate 104. The plurality of pixels 110 each include thepixel circuit 126 (FIG. 2) including at least the selection transistor(not shown), the driving transistor 144 (FIG. 4C) and the light emittingelement 146 (FIG. 4C).

The light emitting element 146 may be, for example, an organic EL lightemitting element. The organic EL light emitting element used as thelight emitting element 146 includes a pixel electrode 148, a commonelectrode 150 and a light emitting layer 152.

The pixel electrode 148 is located in each of the pixels 110. It ispreferable that the pixel electrode 148 includes a highly reflectivemetal layer in order to reflect light generated in the light emittinglayer 152 toward the common electrode 150. The highly reflective metallayer may be formed of, for example, silver (Ag).

The pixel electrode 148 may include a transparent conductive layerstacked on the highly reflective metal layer. Preferably, thetransparent conductive layer may be formed of ITO (indium oxidecontaining tin oxide incorporated thereto), IZO (indium oxide-zincoxide; registered trademark), or the like. The transparent conductivelayer may contain any combination of these materials.

The common electrode 150 is located over the plurality of pixels 110. Apreferable material of the common electrode 150 is light-transmissive sothat light generated in the light emitting layer 152 is transmittedthrough the common electrode 150, and also is conductive. Specifically,it is preferable that the common electrode 150 is formed of ITO (indiumoxide containing tin oxide incorporated thereto), IZO (indium oxide-zincoxide), or the like. Alternatively, the common electrode 150 may be ametal layer having a thickness sufficiently small for the output lightto be transmitted through the common electrode 150 (e.g., layer formedof an alloy of magnesium and silver).

A bank 154 is located between two pixels 110 adjacent to each other. Thebank 154 is provided so as to cover peripheral regions of the pixelelectrodes 148. In this embodiment, the bank 154 is formed of aninsulating material. A usable insulating material may be an inorganicinsulating material or an organic insulating material. An inorganicinsulating material may be, for example, silicon oxide, silicon nitride,a combination thereof, or the like. An organic insulating material maybe, for example, a polyimide resin, an acrylic resin, a combinationthereof, or the like. A combination of an inorganic insulating materialand an organic insulating material may be used. The bank 154 formed ofan insulating material is located, so that shortcircuiting between thecommon electrode 150 and each pixel electrode 148 is prevented at an endof the pixel electrode 148. The bank 154 formed of an insulatingmaterial also insulates the pixels 110 adjacent to each other.

The light emitting layer 152 is held between the pixel electrode 148 andthe common electrode 150. The light emitting layer 152 is formed of anorganic EL material, which emits light when being supplied with anelectric current. Such an organic EL material may be a low molecularweight-type or high molecular weight-type organic material. In the casewhere a low molecular weight-type organic material is used, a holeinjection layer, an electron injection layer, a hole transfer layerand/or an electron transfer layer, for example, may be provided inaddition to the light emitting layer 152. In FIG. 4C, the light emittinglayer 152 is provided so as to cover the pixel electrodes 148 and thebanks 154. The light emitting layer 152 is not limited to being providedin this manner. The light emitting layer 152 may respectively beprovided at positions corresponding to each of the pixel electrodes 148so as to cover a portion of each pixel electrode 148 that is exposedfrom the bank 154. In this case, such light emitting layers 152 coveringdifferent pixel electrodes 148 are formed of organic EL materials thatemit light of different colors.

The sealing layer 132 is provided so as to cover the display region 104a and covers the plurality of pixels 110. The sealing layer 132 isprovided in order to prevent entrance of moisture or the like into theplurality of pixels 110 in the display device 100 from outside of thedisplay device 100. Therefore, it is preferable that the sealing layer132 is formed of an insulating layer that has a low moisturepermeability. It is preferable that the insulating material used for thesealing layer 132 is also capable of flattening the ruggedness caused bythe plurality of light emitting elements 146, the banks 154 and the likelocated below the sealing layer 132. Therefore, it is preferable thatthe sealing layer 132 has a stack structure including an inorganicinsulating layer having a low moisture permeability and an organicinsulating layer capable of flattening the ruggedness.

The first electrode layer 134 is provided on the sealing layer 132 in across-sectional structure. The first electrode layer 134 is provided soas to cover the display region 104 a in a planar structure.

The first electrode layer 134 overlaps the plurality of pixels 110.Therefore, the first electrode layer 134 includes a transparentconductive layer. Preferably, the transparent conductive layer may beformed of ITO (indium oxide containing tin oxide incorporated thereto),IZO (indium oxide-zinc oxide), or the like. The first electrode layer134 may contain any combination of these materials.

Alternatively, the first electrode layer 134 may include a metal layer.In this case, the metal layer may have openings in regions overlappingthe plurality of pixels 110 so as not to block the light emitted in theplurality of pixels 110.

The second electrode layer 136 is provided above the first electrodelayer 134 in a cross-sectional structure. The second electrode layer 136is provided so as to cover the display region 104 a in a planarstructure. The second electrode layer 136 includes a transparentconductive layer. The transparent conductive layer may be formed of anyof substantially the same materials described above regarding the firstelectrode layer 134. Alternatively, like the first electrode layer 134,the second electrode layer 136 may include a metal layer having openingsin regions overlapping the plurality of pixels 110.

The third electrode layer 138 is provided above the second electrodelayer 136 in a cross-sectional structure. The third electrode layer 138includes a plurality of electrodes arrayed in a matrix in a planarstructure.

The third electrode layer 138 includes a transparent conductive layer.The transparent conductive layer may be formed of any of substantiallythe same materials described above regarding the first electrode layer134. In addition, like the first electrode layer 134, the thirdelectrode layer 138 may further include a metal layer having openings inregions overlapping the plurality of pixels 110.

In this embodiment, the plurality of electrodes included in the thirdelectrode layer are each diamond-shaped or triangular. Namely, sides ofeach diamond-shaped electrode, among the plurality of pixels, each makean acute angle with each of the scanning signal line 128 and the videosignal line 130 (described below).

As described below in detail, the third electrode layer 138 is includedin the touch sensor. The plurality of electrodes included in the thirdelectrode layer 138 include electrodes provided for different purposes.As shown in FIG. 5, the plurality of electrodes included in the thirdelectrode layer 138 are classified into three types, specifically,driving electrodes Tx, detection electrodes Rx and dummy electrodes D,in accordance with the purpose thereof.

The driving electrodes Tx are arrayed in the row direction. As shown inFIG. 4B, in this embodiment, a plurality of electrodes located in eachrow, among the plurality of pixels arrayed in the matrix, areelectrically connected with each other via a connection line 164 andthus act as the driving electrodes Tx. The connection line 164 isprovided on an insulating layer 162, which is provided on the thirdelectrode layer 138. The connection line 164 connects the electrodesadjacent to each other via a contact hole formed in the insulating layer162. Thus, the connection line 164 and the detection electrodes Rx(described below) are prevented from being shortcircuited.

Returning to FIG. 5, the detection electrodes Rx are arrayed in thecolumn direction. In this embodiment, a plurality of electrodes locatedin each column, among the plurality of pixels arrayed in the matrix, areelectrically connected with each other and thus act as the detectionelectrodes Rx.

The dummy electrodes D are outermost electrodes among the plurality ofpixels arrayed in a matrix. In this embodiment, the dummy electrodes Dare triangular. The dummy electrodes D are provided in order touniformize the pattern density of the third electrode layer 138 on thedisplay region to decrease the ease of visibility of the third electrodelayer 138. Therefore, the dummy electrodes D may be in an electricallyfloating state.

In this embodiment, the dummy electrodes D do not act as electrodesincluded in the touch sensor. Alternatively, the dummy electrodes D maybe connected with either the driving electrodes Tx or the detectionelectrodes Rx so as to act as electrodes included in the touch sensor.

The piezoelectric material layer 142 is provided between the firstelectrode layer 134 and the second electrode layer 136 in across-sectional structure. The piezoelectric material layer 142 isprovided so as to cover the display region 104 a in a planar structure.

A “piezoelectric material” is a material that is, when being appliedwith a pressure, polarized in a direction of the pressure. Morespecifically, when a pressure is applied to the piezoelectric material,charges appear at a surface of the piezoelectric material as a result ofthe polarization and a voltage is generated inside the piezoelectricmaterial. In this embodiment, a light-transmissive piezoelectricmaterial is used. Specific examples of such a usable piezoelectricmaterial include polylactic acid, poly(vinylidene fluoride), ethylenetrifluoride and the like.

The flexible material layer 140 is provided between the second electrodelayer 136 and the third electrode layer 138 in a cross-sectionalstructure. The flexible material layer 140 is provided so as to coverthe display region 104 a in a planar structure.

Specific example of usable flexible material includes cellulose acetate,polyurethane, acrylic acid, polyethylene (diene-based rubber), siliconerubber, fluorine-based rubber, and the like.

The first electrode layer 134, the second electrode layer 136, the thirdelectrode layer 138, the piezoelectric material layer 142 and theflexible material layer 140 are included in the bending sensor, thepress sensor or the touch sensor. A structure of each of these sensorswill be described in detail with reference to the drawings.

FIG. 5 shows a circuit configuration of the sensor portion of thedisplay device 100 in this embodiment. FIG. 6 shows a method for drivingthe sensor portion of the display device 100 in this embodiment.

[Bending Sensor]

The first electrode layer 134, the second electrode layer 136 and thepiezoelectric material layer 142 are included in the bending sensor. Asshown in FIG. 5, the first electrode layer 134 and the second electrodelayer 136 are each connected with an input terminal of a first amplifiercircuit 156. The bending sensor detects a direction and an amount of thebending of the substrate.

For example, one of the first electrode layer 134 and the secondelectrode layer 136 is supplied with a constant potential whereas theother of the first electrode layer 134 and the second electrode layer136 is kept in an impedance state. The constant potential is, forexample, the ground potential. The other of the first electrode layerand the second electrode layer 136 is kept in, for example, a floatingstate in order to be in a high impedance state. When a force is appliedto the display device 100 in a bending direction in this state, anelectromotive force is generated in the piezoelectric material layer 142held between the first electrode layer 134 and the second electrodelayer 136. The other of the first electrode layer 134 and the secondelectrode layer 136 is in a high impedance state, and therefore, thevoltage between the first electrode layer 134 and the second electrodelayer 136 is changed in accordance with the electromotive force. Such avoltage change is detected, so that the presence/absence and themagnitude of the bending are detected.

[Press Sensor]

The second electrode layer 136, the third electrode layer 138 and theflexible material layer 140 are included in the press sensor. As shownin FIG. 5, the second electrode layer 136 and the third electrode layer138 are each connected with an input terminal of a second amplifiercircuit 158. The press sensor detects a press applied to a regionoverlapping the display region 104 a.

When a pulse-like pressure detection signal is input to the secondelectrode layer 136, the potential of the third electrode layer 138 ischanged by capacitance coupling. When a press is applied to the displayregion 104 a, the thickness of the flexible material layer 140 providedbetween the second electrode layer 136 and the third electrode layer 138is changed, and therefore, the capacitance between the second electrodelayer 136 and the third electrode layer 138 is changed. Specifically, apress applied to the flexible material layer 140 decreases the thicknessthereof, and therefore, the capacitance between the second electrodelayer 136 and the third electrode layer 138 is increased. This increasesthe potential change in the third electrode layer 138 caused by thepressure detection signal. This potential change is detected, so thatthe position and the magnitude of the press are detected.

[Touch Sensor]

The third electrode layer 138 is included in the touch sensor. As shownin FIG. 5, the driving electrodes Tx and the detection electrodes Rx inthe third electrode layer 138 are each connected with an input terminalof a third amplifier circuit 160. The third amplifier circuit 160 isprovided in the number of the combinations of the plurality of drivingelectrodes Tx and the plurality of detection electrodes Rx. In thisexample, one third amplifier circuit 160 is shown as an example. Thetouch sensor detects a touch of a conductor with the region overlappingthe display region 104 a, based on mutual capacitance between theplurality of electrodes.

When a pulse-like touch detection signal is input to, for example, eachrow of the driving electrodes Tx, the potential of the detectionelectrodes Rx is changed by capacitance coupling. In the case where afinger touches any position, the detection electrode Rx forms acapacitance with the driving electrode Tx and also with the finger atthe position of the touch. The capacitance between the driving electrodeTx and the detection electrode Rx is decreased by the capacitancebetween the detection electrode Rx and the finger. Therefore, thepotential change is decreased. This potential change is detected, sothat the position of the touch is detected.

The structure of the sensor portion of the display device 100 in thisembodiment described above. Now, a method for driving the sensor portionof the display device 100 in this embodiment will be described.

FIG. 6 shows a method for driving the sensor portion of the displaydevice 100 in this embodiment. The sensor portion of the display device100 in this embodiment is driven in a time division manner. Morespecifically, as shown in FIG. 6, in this embodiment, the touch sensoris driven to perform touch detection in a first frame period. Next, in asecond frame period following the first frame period, the press sensoris driven to perform pressure detection. Next, in a third frame periodfollowing the second frame period, the bending sensor is driven toperform bending detection. In this manner, the driving is performed in atime division manner. Thus, detection signal components of the sensorsare separated from each other.

The order of driving the sensors of the display device 100 in thisembodiment is not limited to the above order. As described above, in thedisplay device 100 in this embodiment, the second electrode layer 136acts as one electrode of the bending sensor and also as one electrode ofthe press sensor. The third electrode layer 138 acts as one electrode ofthe press sensor and also as one electrode of the touch sensor. Namely,the sensors merely need to be driven such that the bending sensor andthe press sensor are not driven at the same time and the bending sensorand the touch sensor are not driven at the same time. The touch sensorand the bending sensor may be driven at the same time. Namely, the firstframe period and the third frame period may have an overlapping period.

[Application Examples]

Application examples of the display device 100 in this embodiment willbe described. FIG. 7A and FIG. 7B are each a perspective view showing anapplication example of the display device 100 in this embodiment. FIG.7A shows a state where the display device 100 is bent such that thedisplay surface is convexed. FIG. 7B shows a state where the displaydevice 100 is bent such that the display surface is concaved. In thecase where the display device 100 is bent such that the display surfaceis convexed, the displayed image is enlarged. In the case where thedisplay device 100 is bent such that the display surface is concaved,the displayed image is reduced. Thus, the displayed image may beenlarged or reduced in association with the direction of the bendingdetected by the bending sensor.

The structure of the display device 100 in this example is describedabove. The display device 100 in this embodiment is a flexible displaydevice including sensors performing touch detection, pressure (press)detection and bending detection, and allowing detection signals detectedby these sensors to be separated from each other.

In the display device 100 in this embodiment, the second electrode layer136 is shared by he press sensor and the bending sensor. The thirdelectrode layer 138 is shared by the touch sensor and the bendingsensor. The detection signals are separated from each other by drivingthe sensors in a time division manner. This simplifies the structure ofthe display device 100, which reduces the production cost. In addition,the sensor portion of the display device 100 is made thinner and thus ismade sufficiently flexible.

Embodiment 2 [Detailed Structure]

FIG. 8 is a plan view showing a structure of a sensor portion of adisplay device 200 in this embodiment. FIG. 9 is a cross-sectional viewschematically showing a structure of the display device 200 in thisembodiment. Specifically, FIG. 9 shows a cross-section taken along lineI-I′ in FIG. 8. The display device 200 in this embodiment s differentfrom the display device 100 in embodiment 1 in the structure of thefirst electrode layer 134.

Specifically, the first electrode layer 134 in this embodiment includesa plurality of electrodes arrayed in at least one of a row direction anda column direction. In this embodiment, the first electrode layer 134includes nine electrodes. More specifically, three electrodes arearrayed in the row direction, and three electrodes are arrayed in thecolumn direction.

Such a structure allows a more complicated bending operation to bedetected. More specifically, the sensor portion of the display device200 detects whether the display device 200 has been bent or not, themagnitude of the bending, and also the position of the bending.

[Application Example]

An application example of the display device 200 in this embodiment willbe described. FIG. 10 is a perspective view showing an applicationexample of the display device 200 in this embodiment. FIG. 10 shows thedisplay device 200 in a state where a portion thereof in the vicinity ofone end is rolled to be cylindrical. An image is displayed in a part ofthe display region 104 a that is visible in this state. Namely, no imageis displayed in a part of the display region 104 a that is madeinvisible as a result of the display device 200 being rolled to becylindrical. In this manner, a plurality of parts of the display region104 a may each be switched to a display state or to a non-display statein association with the magnitude of the bending detected in the part.

The structure of the display device 200 in this embodiment is describedabove. The display device 200 in this embodiment is a flexible displaydevice including sensors performing touch detection, pressure (press)detection and bending detection, and allowing detection signals detectedby these sensors to be separated from each other. In addition, thedisplay device 200 in this embodiment detects a complicated bendingoperation.

Preferable embodiments of the present invention have been described.These embodiments are merely examples, and the technological scope ofthe present invention is not limited to any of the above-describedembodiments. A person of ordinary skill in the art would make variousalterations or modifications without departing from the gist of thepresent invention. Such alterations and modifications should beconstrued as being encompassed in the technological scope of the presentinvention.

The above-described embodiments may be combined in any appropriatemanner unless contradicting each other. The devices described above inembodiments according to the present invention may have an element addedthereto, or deleted therefrom, or may be changed in design optionally bya person of ordinary skill in the art. The methods described above inembodiments according to the present invention may have a step addedthereto, or deleted therefrom, or may be changed in a conditionoptionally by a person of ordinary skill in the art. Such devices andmethods are encompassed in the scope of the present invention as long asincluding the gist of the present invention.

Even functions and effects that are different from those provided by theabove-described embodiments but are obvious from the description of thisspecification or are easily expectable by a person of ordinary skill inthe art are naturally construed as being provided by the presentinvention.

What is claimed is:
 1. A display device comprising: a flexible substratehaving a display region, the display region including a plurality ofpixels, each of the plurality of pixels having a display element; asealing layer covering the plurality of pixels; a first, a second and athird electrode layer on the sealing layer, each of the first, thesecond and the third electrode layer is located on a different layer; afirst insulating layer between the first electrode layer and the secondelectrode layer; and a second insulating layer between the secondelectrode layer and the third electrode layer.
 2. The display deviceaccording to claim 1, wherein the first electrode layer is divided intoa plurality of first electrodes, the third electrode layer is dividedinto a plurality of third electrodes, and an area of each of theplurality of third electrodes is smaller than an area of each of theplurality of first electrodes.
 3. The display device according to claim1, wherein the first insulating layer is a piezoelectric layer.
 4. Thedisplay device according to claim 1, wherein the second insulating layeris a flexible material layer.
 5. The display device according to claim1, wherein the first electrode layer, the second electrode layer and thefirst insulating layer are configured to include a bending sensordetecting a direction and an amount of a bending of the flexiblesubstrate, the second electrode layer, the third electrode layer and thesecond insulating layer are configured to include a press sensordetecting a pressure applied to a region overlapping the display region,an uppermost layer of the first, the second and the third electrodelayer includes a plurality of electrodes arrayed in a matrix, theplurality of electrodes are configured to include a touch sensordetecting a touch of a conductor with the region overlapping the displayregion.
 6. The display device according to claim 1, wherein at least oneof the first, the second and the third electrode layer includes atransparent conductive layer.
 7. The display device according to claim1, wherein at least one of the first, the second and the third electrodelayer includes a metal layer having openings with respect to regionsoverlapping the plurality of pixels.
 8. The display device according toclaim 5, wherein each of the press sensor and the touch sensor overlapsthe display region.
 9. The display device according to claim 8, whereinthe bending sensor overlaps the display region.